Preparation and properties of polyamide-imides derived from 1,3-bis(4-aminophenoxy)benzene, trimellitic anhydride, and various aromatic diamines

A diamine, 1,3-bis(4-aminophenoxy) benzene (II), was synthesized in two steps; fist from the condensation of resorcinol with p-chloronitrobenzene in the presence of potassium carbonate, producing I,3-bis(4-nitrophenoxy) benzene (I), followed by hydrazine hydrate/Pd-C reduction. A two imide rings-preformed dicarboxylic acid, 1,3-bis(4-trimellitimidophenoxy)benzene (III), was prepared from the condensation of diamine II and trimellitic anhydride in 1:2 molar ratio. A series of structurally new polyamide-imides (V_a-p) were directly synthesized from the diacid III and various aromatic diamines (IV_a-p). The resultant polyamide-imides had inherent viscosities between 0.56-1.39 dl/g. All polymers, except some derived from diamines with p-phenoxy structure, showed excellent solubility. Some polymer resulted in tough or flexible transparent films. Dynamic TG data indicated that all polymers possess excellent thermal stability with no significant weight loss up to the temperature of approximately 450 °C in nitrogen, and their 10% weight loss temperature was recorded in the range of 489-577 °C. Measurements of wide-angle X-ray diffraction revealed that some polymers derived from p-phenoxy group-containing diamines showed crystalline patterns.